Hi Tauqir_Hassan,
Unfortunately I am having the same problem as you (my module is BG95-M3 which is similar to BG96). I have contacted the local support in my region and have not had a response yet. I will share the solution if I find one.
Since the AT+QMTOPEN command does not forward an error code (only the number -1, which means Failed to open network), what I tried to do was to ping the DNS address of my AWS server using the AT+QPING command (in your case it would be AT+QPING=0, “a19jyibremb4gx-ats.iot.us-west-2.amazonaws.com”). When I did this I got error 565, which means DNS parser failed, and also sometimes I got operation time out error 569. I think our problem is before the MQTTS (or HTTPS) layer, because both of them travel over the TPC/IP layer. Have you tried ping the DNS address of your server, or even Google’s address? Because I think the problem might be that our modules are not finding the DNS address (or even the IP address number) of our End Point in the network.
If I find the fix I will forward it to you, please, if you find it also share it, because I am suffering a lot from this problem too.